The compound 5-methoxy-2-[[(4-methoxy-3,5-dimethyl-2-pyridinyl)methyl]sulfinyl]-1H-benzimidazole, which has the generic name omeprazole, was described for the first time in the document EP 5.129-A. Omeprazole is a sulphoxide that contains an asymmetric center in the sulphur atom, and therefore exists as a racemic mixture of two enantiomers, R-omeprazole and S-omeprazole. The R configuration corresponds to the (+)-enantiomer and the S configuration to the (−)-enantiomer.
Omeprazole is susceptible to degradation in acidic and neutral media. Its stability is also affected by other factors such as humidity, temperature and organic solvents. Certain salts of omeprazole are described in EP 124.495-A where it indicates that they are more stable during storage than the neutral form of omeprazole.
Omeprazole and its alkaline salts are effective inhibitors of gastric acid secretion and, therefore, are useful for the prevention and treatment of gastric acid-related disorders and inflammatory gastrointestinal diseases (e.g., gastric ulcer, duodenal ulcer, reflux esophagitis and gastritis). In addition, they can also be used for the treatment of other gastrointestinal disorders where a cytoprotectant and/or anti-gastric secretion effect is desired (e.g., in patients with gastrinomas, in patients with acute upper gastrointestinal hemorrhage, and in patients with a history of chronic and excessive alcohol consumption).
EP 652.872-A describes the magnesium salt of S-omeprazole, the formula of which is included below, and indicates that it possesses pharmacokinetic and metabolic properties that give it an improved therapeutic profile. There are other documents that describe different solid forms of magnesium salt of S-omeprazole. EP 984.957-A describes a trihydrate form of magnesium salt of S-omeprazole. WO 04/20436 describes a hydrate of magnesium salt of S-omeprazole in amorphous solid form. Finally, EP 1.375.497-A describes a magnesium salt of S-omeprazole with a grade of crystallinity of less than 67% and a magnesium salt of S-omeprazole with an amount of organic solvent of less than 7%.

The different solid forms of a pharmaceutically active ingredient can have different characteristics, and offer certain advantages, for example with regard to solubility or bioavailability. Thus, the discovery of new solid forms allows for improving the characteristics of the pharmaceutical formulations of the active ingredients, since some forms are more adequate for one type of formulation, and other forms for other different formulations. Furthermore, depending on the therapeutic indications, one or another pharmaceutical formulation may be preferred, hence omeprazole may be commercialized, for example, in the form of capsules and vials, and S-omeprazole as gastroresistant tablets. It may hence be of interest to have new solid forms of magnesium salt of S-omeprazole.